1. Field of the Invention
The present invention relates to instruments for use in surgical applications, and more specifically, to a rod coercer for positioning a rod into a surgical implant during a spinal fixation procedure.
2. Related Art
In spinal fixation surgery, a rod and a set of vertebral implants (e.g., pedicle screws) are often used to correct spinal deformities. In such procedures, the rod is often bent to a desired shape using an appropriate rod bender. Then, a surgeon installs the implants in selected vertebral bodies along the length of the spine. Each implant usually includes a head which is shaped to receive a portion of the rod. After the implants have been installed, the rod is seated or “reduced” into the head of an implant, using a device which applies force to the rod and the implant, so that the implant and its associated vertebral body, and the rod, are drawn together, and a portion of the rod is seated in the head of the implant. Once the rod has been reduced into the head of the implant, a cap is engaged with (e.g., threaded into) the head of the implant and tightened to retain the rod in the head of the implant. This process may be repeated for each of the remaining implants, as needed, until the rod has been reduced into all of the implants. Once the procedure is complete, the spine conforms to the shape of the rod, to correct the spinal deformity. Thus, it is very important in such procedures to properly reduce a spinal rod into its associated implants.
Various devices for reducing a rod into an implant are known. One example is a simple forceps-type apparatus which includes articulating forceps branches and a bifurcated gripping nose which pivotally grips the head of an implant. When the forceps branches are closed and the pivotal grip is established, the device can be pivoted with respect to the implant to contact a rod and to exert force on same using a fulcrum arrangement, so as to reduce the rod into the head of the implant. Other devices include rod reducers having axially-aligned, concentric sleeves that move axially with respect to each other. Such devices include a pistol and trigger grip, as well as a ratchet mechanism interconnected with the trigger to urge one of the sleeves axially relative to another sleeve, causing prongs of the inner sleeve to grip an implant and the outer sleeve to reduce the rod into the implant. Another device includes a forceps-type instrument which grips an implant, and a separate articulating device which attaches to the forceps-type instrument and which pivots to reduce a rod into the implant.